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Data on weaning weight of 4179 lambs born from 1005 ewes and 225 rams of Lori-Bakhtiari
breed, collected during 1999 and 2003 by the Lori-Bakhtiari sheep breeding station, located in
Chaharmahal-o-Bakhtiari province, were employed to estimate (co)variance components and
genetic parameters for total weight of lambs weaned per ewe joined in the first, 2nd, 3rd, 4th
and 5th parities. Estimates were carried out through Restricted Maximum Likelihood
procedures, using univariate, repeated-records, and multivariate Animal Models. The mean
total weight of lambs weaned per ewe joined in the first, 2nd, 3rd, 4th and 5th parities were
28.95±5.70, 30.86±6.99, 31.89±8.41, 32.29±8.78 and 32.36±8.01 Kg, respectively. In univariate
analysis, two different animal models were fitted to investigate direct additive genetic and
service sire effects. Based on this analysis, direct heritability for total weight of lambs weaned
per ewe joined varied from 0.090 (3rd parity) to 0.182 (4th parity). The corresponding estimates
for service sire effect were very low and close to zero. Estimates of heritability and repeatability
from repeated-record analysis were 0.104 and 0.332, respectively. Additive genetic correlations
between different parities of total weight of lambs weaned per ewe joined were positive, ranging
from 0.359 (between first and 5th parity) to 0.844 (between 4th and 5th parity). The
corresponding estimates for phenotypic correlations ranged from 0.300 (between 2nd and 5th
parity) to 0.667 (between 4th and 5th parity).